Zest one lemon and squeeze the juice from both.  Cover chicken with the olive oil and lemon juice.  Marinate for 2-3 hours.  Toss together sea salt and zest.  Remove chicken from marinade and sprinkle with lemon salt and white pepper.  Grill on each side for 7-10 minutes.  Meanwhile, melt margarine in a large skillet.  Simmer the onions on low for about an hour, adding chicken stock as needed to keep moist.  When onions are soft, add blueberries and cook slowly for about 20 minutes.  When almost a jam, season to taste with salt and white pepper and serve over lemon chicken.